1. Field of the Invention
The present invention relates to an electronic endoscope having a video-scope. In particular, it relates to a signal process for displaying a color image.
2. Description of the Related Art
In an electronic endoscope, a video-scope with an image sensor is inserted into a body cavity such as a stomach, and image-pixel signals corresponding to an observed image are read from the image sensor. In a video-processor, video signals are generated on the basis of the image-pixel signals and are output to a monitor, so that an observed image is displayed on the monitor. As for video signals, in addition to analog image signals, digital image signals are generated. For example, digital component video signals composed of luminance signals (Y) and color difference signals (U, V) are generated from primary color (R, G, B) digital video signals. A signal process for generating the video signals is performed while synchronizing clock pulse signals, which are output from a clock pulse generator.
A phase of the clock pulse signals is occasionally reversed; in other words, a high level and a low level of the clock pulse signals are switched, due to characteristics of the power supplying circuit or of a connection of the video-scope. When the phase of the clock pulse signals is reversed, a phase of the generated digital component video signals is also reversed, so that an observed image in which color is reversed is displayed on the monitor. For example, a reddish observed image becomes a bluish observed image.